A steam cooker generally consists of the cooking chamber and a source of steam. Heat from the steam transfers directly to food items placed in the cooking chamber.
Cooking food in the presence of steam has been found to be very efficient and to have a minimal effect on taste, texture, color and other characteristics of the food. The moist cooking environment provided by the steam, inhibits the dehydration of the food being processed. Dehydration is often a problem in radiated heat and convection air type ovens.
Two types of steam processors are generally available today. One type of processor operates in a convection mode in which steam is introduced into a cooking compartment and condensate is allowed to leave the compartment through a drain, generally maintained at ambient pressure. In this type of processor, the cooking compartment is maintained at substantially atmospheric pressure and the low pressure steam circulates around the food trays.
In another type of steam processor, the cooking/heating of the food items occurs under pressure. In this type of processor, the cooking cabinet is sealed and the steam is introduced into the compartment under pressure. Generally, the compartment is pressurized in the range of 10psi.
With a convection type steamer, the door can be opened at any time during the cooking process to visually check the food being processed. With a pressure-type steamer, the cooking time for a given item is generally reduced. However, because the cabinet is maintained under pressure, the door must be locked and sealed until the end of the cooking cycle. It has also been found that certain items and/or certain operators prefer convection type steamers for certain food items and pressure-type steamers for other items.